North Korea came in from the cold yesterday, after handing over a declaration of its nuclear programme to Chinese officials. Even though the declaration falls short of what the US once demanded, President George Bush said he would lift US trade sanctions and notify Congress that he intends to take North Korea off the state department list of nations that sponsor terrorism. One of the spokes seems to have come off the axis of evil.

There was no shortage of irony in yesterday's statements. With the clock ticking on his remaining months in power, North Korea could well go down as Mr Bush's sole foreign policy success. And yet it was achieved only after a dramatic U-turn, from which John Bolton, a former leading neoconservative, is still smarting. Mr Bolton's muscular treatment of North Korea was jettisoned, and the state department dusted off a policy of pragmatic engagement pursued by Bill Clinton a decade earlier. Washington was jolted into action by a nuclear test. The device only partially exploded, but the diplomatic shockwave travelled the world. Rogue states take note: if you have a weapon of mass destruction, use it as soon as you can, because only then will anyone take you seriously.

Christopher Hill, the US negotiator whose triumph this is, cautions against drawing too many conclusions. Unlike Iran, North Korea is on its knees, one flood or typhoon away from mass starvation. Another factor is psychological: North Korea's awareness of its own isolation. It is surrounded by booming economies and selling off the secrets of its nuclear programme is the only card the regime has left to play.

This is not the end of the North Korean story, but the start of another, equally anguished phase for the peninsula as a whole. The economic gap between north and south is many times wider than that which existed between east and west Germany when the wall came down. A sudden collapse of the regime in Pyongyang is the last thing Seoul needs. The probable ending of the North Korean nuclear programme (questions over the number of bombs created and a parallel programme of uranium enrichment are still to be answered) will not only lead to the ending of the last conflict of the cold war - it is an opportunity to learn from the blunders made in nation-building in recent history.

Both the implosion of the Soviet Union and the overthrow of Saddam Hussein should have taught the west the limitations of trying to fashion other countries in our image. Demolition, alone, is not enough. It will take more time and skill to construct a viable new order, one which genuinely serves the needs of the Korean peninsula.